Marker light

ABSTRACT

A flexible liquid tight marker light that comprises a light source encapsulated by injection molding a light transmitting elastomeric polymer to form a protective casing which further includes an imbedded wiring harness electrically connected to said light source and imbedded structural members that protect the light source from excessive flexing and impacts. The wiring harness and structural members provide heat sink means for the light source. The casing is comprised of variable durometer tinted polyurethane elastomers with light diffusing pigments added. Diverging optics are molded into the casing outer surface.

FIELD OF THE INVENTION

[0001] This invention is directed to marker lights, and moreparticularly to light emitting diode type marker lights that areflexible and liquid tight and are resistant to damage caused impacts,abrasion or exposure to extreme environmental elements.

BACKGROUND OF THE INVENTION

[0002] This invention generally relates to impact and shock resistantmarker lights comprising encapsulated light sources. Marker lights usedin applications such as off road vehicles are subjected to extreme abusesuch as vibration created by traversing rough terrain and directexposure to the elements such as rain, mud and dust plus an occasionalimpact with a tree branch or a vehicle crash. In particular, it relatesto such lights wherein one or more light emitting diode (LED) lightsources and a structural protective member with an integral wiringharness surrounding the LED's are encapsulated by injection molding atransparent or semi-opaque thermoplastic elastomeric resin casing aroundthem.

[0003] 1. Description of the Prior Art

[0004] Marker lights currently utilize short life span incandescentbulbs as the primary means for producing light. Incandescent bulbsrequire high wattage for operation due to their inefficient nature ofenergy to light conversion as most energy ends up as waste heat. Mostincandescent type marker lights have a removable lens to allow bulbreplacement and thus are not sealed to be completely water, dust or mudproof Marker lights with incandescent filament type bulbs exhibit areduction in bulb life when exposed to vibration, water and impactsencountered during off road use. Filament lamps have many drawbacks suchas high power consumption, generating large amount of heat and filamentbreakage, the lamps per se being large and heavy. Existing marker lighthousings are constructed of semi-rigid plastics which are not inherentlyflexible, have low izod impact strengths and thus demonstrate apropensity to substain permanent damage during impacts. Incandescenttype marker lights are also large and bulky due to the inner housingdesign which generally utilizes a metal carrier to hold the hot bulb andact as heat sink while also providing a means for bulb retention andreplacement. The metal carrier that secures the bulb has a tendency tocorrode over time due to water condensation in the bulb housing. Thecorroded electrical contacts of the metal carrier can produce a degradedintermittent light circuit connection or a possible open circuit.Incandescent marker lights usually have a separate transparent tintedlens assembly surrounding the incandescent bulb that is molded from lowimpact resistant styrene, polycarbonate or acrylic and thus is fragileand breaks easily when subjected to impacts. Therefore it would bebeneficial to have an improved marker light without the problemsdescribed.

SUMMARY OF THE INVENTION

[0005] The purpose of the present invention is to provide a zeromaintenance marker light of the aforesaid type that is impact, shock,and abrasion resistant while also increasing the overall marker lightoperational life, while reducing weight and power requirements. Themarker light design must be producible utilizing high volume productionmethods such as injection molding, wave soldering and pressworkoperations. This purpose is met by this invention, which ischaracterized by the fact that the marker light casing is injectionmolded utilizing a tough elastomeric plastic polymer that is moldedaround the LED's, the LED protective structure and LED wiring harnesssuch that the marker light constitutes a non-dismountable whole. Thisresults in a completely liquid tight encapsulation with combinedelectrical insulation and resistance to extreme mechanical stresses suchas impacts, vibration and abrasions. Since the light output of an LED isa reduced by high humidity, the complete embedment of the LED by athermoplastic elastomer prevents moisture ingress. The LED's with theirattached flexible wiring harness and protective structure are insertinjection molded around a flexible thermoplastic elastomer. The flexiblecomposite assembly created, allows the thermoplastic elastomer casing toattenuate energy during impacts without affecting the LED's or theirassociated electrical connections. The marker light casing is composedof highly abrasion resistant elastomeric polymers that do not mar orscratch easily and readily retain their initial shape after impacts. TheLED's used in the marker light are classified as solid statesemiconductor devices that have a mean time between failure ofapproximately 100,000 hours and are not damaged by vibration or shockloads. For added attractiveness and appeal, the thermoplastic elastomercasing can be molded using any semi-opaque color scheme provided itmeets optical requirements of SAE J576. The semi-opaque colored casingdiffuses the intense focused LED light, increasing the viewing angle andlowering the on axis LED intensity producing a more homogenous anduniform light distribution. The marker light output can also be furtherenhanced by molding a lens into the casing to diverge the LED lightoutput to produce a marker light high in luminance and wide in viewingwhile eliminating glare complaints and reducing the number of lightemitting diodes required. The LED's used in the marker light are veryefficient devices as they operate on approximately 20 percent of thepower required by incandescent bulbs. Vehicle weight is a major designconsideration for on-off highway vehicles. Lower weight vehicles havebetter maneuverability and operator control plus reduced energyconsumption and increased vehicle performance. A vehicle's alternatorpower output can be reduced using LED lighting technology thus reducingoverall vehicle weight. When LED based marker lights are used asemergency flashers utilizing only battery power, the operation time canbe increased from two to four times over incandescent lightingtechnology. This feature provides a safety improvement as well asreducing the likelihood of a dead battery. LED's are solid state devicesso they turn on and off in tens of nanoseconds compared to about 200milliseconds for an incandescent bulb. This provides the end user asafer signalling device that turns on approximately one car lengthquicker at highway speeds. Other details and advantages of the presentinvention will become apparent as the following description of thepresently preferred embodiments of practicing the invention proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006]FIG. 1 Is a front view an embodiment of a marker light mounted asa signal device on the rear section of a motorcycle;

[0007]FIG. 2 is a front view of a marker light constructed in accordancewith the present invention;

[0008]FIG. 3 is a side view of the marker light of FIG. 2;

[0009]FIG. 4 is a front view of a marker light wiring harnessconstructed in accordance with the present invention;

[0010]FIG. 4A is a cross-sectional view taken at line 4A-4A of FIG. 4;

[0011]FIG. 5 is a rear view of a second embodiment of a marker lightconstructed in accordance with the present invention;

[0012]FIG. 6 is a side view of the marker light of FIG. 5;

[0013]FIG. 7 is a rear view of the marker light wiring harness of FIG. 5constructed in accordance with the present invention;

[0014]FIG. 8 is a front partial sectional view of a marker light mountedto a vehicle body;

[0015]FIG. 9 is a side partial sectional view of the marker light ofFIG. 8;

[0016]FIG. 10 is a rear view, partially in section, of a secondembodiment of a marker light mounted to a vehicle body;

[0017]FIG. 10A is a side sectional view taken at line 10A-10A in FIG.10;

[0018]FIG. 11 is a schematic diagram of the marker light wiring harnessdepicted in FIG. 7; and

[0019]FIG. 12 is a schematic diagram of the marker light wiring harnessdepicted in FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

[0020] The marker light 1 consists of LED's 8, 8 a connected to aflexible wiring harness assembly 6 that is insert molded into aninjection molded thermoplastic elastomeric case 10 with integral moldedin lenses 23 for light divergence. The wiring harness assembly 6includes of a pair of laterally spaced apart, opposite chargeable,abrasion resistant, high tensile strength, nylon coated, multi-strandedstainless steel cables 2 and 3 that run longitudinally to the injectionmolded thermoplastic elastomeric case 10. The cables 2, 3 haveuninsulated stripped cable portions 2 a and 3 a which act as terminalsfor conduction of electricity. The stripped cable portion 2 a is apositive conductor and the stripped cable portion 3 a is a negativeconductor. Stripped cables 2 a,3 a have crimped on generally cylindricalcable stops 4 that act as a strain relief to prevent cable 2, 3 movementunder tension loading and cable 2, 3 pullout during extreme case 10flexure and act as locational guides and tie down points during theinsert injection molding process. The cable stops 4 can be made from amalleable medium strength material such as copper or aluminum. The cablestop 4 can be used as a electrical terminal connection to transmitelectricity from the stripped cable portion 2 a, 3 a to a flat braidedcopper LED connection strip 17 when the cable stop 4 is crimped aroundboth the flat braided copper LED connection strip 17 and stripped cableportion 2 a, 3 a forming a permanent interference fit electricaltermination as shown in FIG. 7. The LED's 8, 8 a are electricallyconnected together in series or parallel to form an array using eithercrimp type connections or wave soldering techniques depending on thetype of LED 8,8 a used. The flat braided copper LED connection strip 17is attached to the LED terminal leads 22 by solderjoints 18. Snap LED'sBa manufactured by Hewlett Packard, have large deformable wing typeterminal leads 22 a that can be crimp formed around the stripped cable 2a,3 a forming an interference fit as shown in FIG. 4A. Thermal andelectrically conductive epoxy or silicone adhesive (not shown) may beplaced between the wing type terminal leads 22 a and stripped cables 2a, 3 a for enhanced electrical conductivity, heat transfercharacteristics and joint reliability. The wiring harness assembly 6 isdesigned to be a thermal heat sink for the LED terminal leads 22, 22 ato maximize heat transfer from the LEDs 8, 8 a. An ideal drive circuitwill provide the same current to the LED's 8, 8 a regardless of ambienttemperatures and power source 26 voltage variances. To balance circuitcost and complexity, the series LED drive circuit 27 consists of acurrent limiting resistor 25 and a positive temperature coefficientresistor (PTC) 29. In the series LED drive circuit 27, the input currentto the LED's 8 varies as the power source 26 positive input voltage 30deviates. Current control characteristics improve as the currentlimiting resistor 25 increases in value and fewer LED's 8 are used inseries. For Vehicle applications, where battery voltage is approximately13 volts, four LED's 8 in series is a good compromise between currentcontrol, heat generation and minimum turn on voltage. Temperaturecompensation is achieved by incorporating a PTC resistor 29 in theseries LED drive circuit 27 so when ambient temperatures increase, theforward current to the LED's 8 decreases. This allows the LED's 8 to bedriven at a higher forward current by reducing the amount of currentderating. Battery powered marker lights 1 for mountain bikes require alow voltage battery power (1.5-3 volts DC) source. The low voltageparallel LED drive circuit 28 consists of a power source 26, currentlimiting resistor 25, a PTC resistor 29 and a silicon diode 31 forreverse voltage protection in series with the LED's 8 a. The currentlimiting resistor 25 and PTC resistor 29 should be located away from theLED's 8, 8 a to prevent thermal problems. In the series LED drivecircuit 27 and the parallel LED drive circuit 28 proper thermalmanagement techniques and drive current selection are critical tomaximize the light output of the LED's 8, 8 a.

[0021] Protecting and adding structural integrity to the case 10surrounding the LED's 8, 8 a between two of the cable stops 4 andlocated around each stripped cable portion 2 a, 3 a is a roll formedtube 5 formed of steel. The roll formed tubes 5 act as structuralmembers to protect the LED's 8, 8 a by preventing excessive case flexureand deformation in the area where the LEDs 8, 8 a are imbedded in thethermoplastic elastomeric case 10. Large LED 8, 8 a light arrays mayinclude roll formed tubes 5 running perpendicular to each other foradditional structural support. There are many methods to electricallyconnect and structurally protect the LED's 8, 8 a and these are but twoexamples that maximize the thermoplastic shot size used to mold the case10 while minimizing the insert molded wiring harness volume to obtainhigh impact energy absorption characteristics while minimizing themarker light 1 weight. The wiring harness 6 is coated with adhesives(not shown) to provide an interlocking bond between the adhesives andthe thermoplastic elastomer during insert molding. The adhesive tothermoplastic elastomer bond prevents the wiring harness 6 frommicroscopically separating from the thermoplastic elastomer during case10 flexure. This improves the overall marker light 1 structural dynamicsby elimination or reduction of fatigue at contact points. Shock loadsare more uniformly distributed over the entire wiring harness 6 thusmaking the marker light 1 less susceptible to sudden damaging loads Theadhesive layer also adds cushioning and creates an additional protectivemoisture barrier between the LED's 8, 8 a and the case 10. A two partadhesive system utilized to provide rubber tearing bonds and outstandingenvironmental resistance are Chemlock 219 and 213 manufactured by LordChemical Products. Chemlock 219 can be used as a primer for Chemlok 213adhesive as their properties are complementary. When using a two coatsystem, optimum bond performance requires pre-baking of the wiringharness 6 before insert molding. Pre-bake can be as long as 16 hours at250° F. or as high as 325 for 2 hours when used with 219 as a primer.But it should be appreciated that the operating parameters of the methodfor each system should be adjusted empirically to optimize the overallmarker light 1 performance. The case 10 can be molded from polyether orpolyester based thermoplastic polyurethanes (TPU) with polyester basedTPU's offering excellent toughness and resistance to oils and chemicalswhile polyether based TPU's offer excellent flexibility, hydrolyticstability and low temperature properties. Multi-shot injection moldingtechniques allow different durometer resins to be utilized incombinations to form a variable durometer case 10 that has areasdiffering in hardness and flexibility to optimize LED 8, 8 a protectionwhile allowing increased flexure in areas designed to absorb impactenergy. Common TPU's that can be used include Pellethane by DowChemical, Texin by Bayer Plastics or Estane by B.F. Goodrich. Pellethanethermoplastic elastomers are the preferred polymers for vehicle lightingapplications due to their balance of chemical/oil resistance,ultraviolet light protection, toughness over temperature extremes, easeof processing and refractive indexes that are similar to traditionallens materials such as polycarbonate. The thermoplastic elastomers areinjection molded at temperatures lower than the thermal distortiontemperature of the LED's 8, 8 a. Injection molding process parametersare dependent on mold design and the type of injection molding processused and thus must be optimized for each application. The thermoplasticelastomer case 10 can be molded from pigmented and tinted TPU's thatdiffuse the intense focused LED 8, 8 a light, producing a wider viewingangle and a more uniform light distribution while also producing amarker light 1 that matches the color of the vehicle. Complete lightattenuation on one side of the case 10 can be achieved by adding asubstantial amount of pigments. The LED 8, 8 a radiation pattern can bedirected with lenses 23 molded into the case 10 to provide a uniformlight output over wide viewing angles. Lens 23 types such as pillow,fresnel and convex can be molded into the case 10 to provide divergingoptics. A marker light 1 mounting method that allows disengagement ofthe marker light 1 from the vehicle body 9 during impingement withanother structure is desired. Two molded in, oppositely opposed,semicircular notches 7 located near the case 10 extremity where thecables 2, 3 exit, are utilized to secure the case 10 to the socket 13when the case is installed in the U-shaped member 19 or case mount 20.Spring pins 24 are installed in the case mount 20 to form crenulationsinside the socket 13 to capture and hold the case 10. The case 10, dueto its deformable elastomeric material properties, can be press fit byhand into the socket 13 and is thus retained by the interference createdby the spring pin 24 projection and the semi-circular notches 7 in thecase 10. In an alternate form, the case 10 is disposed into the socket13 of a U-shaped member 19 and is fastened by a nylon tie wrap 12 thatgirds around the U-shaped member notches 21 and over the semi-circularnotches7 to secure the case10 to the U-shaped member 19. A compressiblefoam pad 14 is adhesively attached to the back of the U-shaped member 19to provide cushioning and conformance to an irregular shaped vehiclebody 9. The case mount 20 and U-shaped member 19 are fastened to avehicle body 9 utilizing common fastening methods such as screws 11,washers 15 and nuts 16. The U-shaped member 19 is preferably stamped andformed using common pressworking techniques and due to product weightbeing a major design constraint, aluminum is the material of choice. Thecase mount 20 is designed to be more attractive in appearance and thuscan be produced from aluminum using die casting methods or be injectionmolded from a high impact strength, glass filled, reinforced plastic. Itis to be understood that various changes and modifications may be madefrom the preferred embodiments discussed above without departing fromthe scope of the present invention, which is established by thefollowing claims and equivalents thereof

The inventor claims:
 1. A marker light comprising: a light sourcecomprising at least one light-emitting diode, an electrical connectionto a source of electrical power and said light source, and anelastomeric casing bonded to said light source to attenuate transmissionof impact energy, said casing having a generally light-transmittingregion for transmission of light from the light source.
 2. A markerlight according to claim 1, wherein said casing comprises at least oneinjection-moldable polyurethane elastomer.
 3. A marker light accordingto claim 1, wherein said casing light transmitting region has an outersurface configured to define at least one diverging optic.
 4. A markerlight according to claim 1, wherein at least a portion of said casing ispigmented with a light diffusing material.
 5. A marker light accordingto claim 1, and further comprising: at least one structural memberdisposed in said casing and at least partially surrounding said lightsource to protect the light source from excessive flexing and impact. 6.A marker light according to claim 5 wherein said structural membercomprises a heat sink means for the light source.
 7. A marker lightaccording to claim 1, wherein said electrical connections compriseinsulated wire cables with attached strain relief structure.
 8. A markerlight according to claim 1, wherein said casing has one tinted generallytransparent side and one pigmented light blocking darker side.
 9. Amarker light according to claim 1, and further comprising: generallyrigid elongate members to modify flexual characteristics of said casingto prevent impact damage to said light source.
 10. A marker lightaccording to claim 1, wherein the casing comprises a plurality ofregions of differing hardnesses and flexibilities.
 11. A marker lightaccording to claim 1, wherein said casing comprises variable durometerelastomeric polymers.
 12. A marker light according to claim 1, andfurther including: casing mounting structure to support the casing bysaid electrical connection when the casing is subjected to substantialimpacts.
 13. A liquid-tight impact resistant flexible marker lamp,comprising: at least one wiring harness, a plurality of light emittingdiodes disposed on and electrically connected with the wiring harness,an injection molded casing wherein said at least one wiring harness isembedded, and at least two electrical leads protruding from said casing.14. A liquid-tight impact resistant flexible marker lamp according toclaim 13, wherein said casing comprises at least one injection-moldablepolyurethane elastomer.
 15. A liquid-tight impact resistant flexiblemarker lamp according to claim 13, wherein a portion of the casing outersurface is con figured as a diverging optic.
 16. A liquid-tight impactresistant flexible marker lamp according to claim 13, wherein at least aportion of said casing is pigmented with a light diffusing material. 17.A liquid-tight Impact resistant flexible marker lamp according to claim13, and further compromising: at least one structural member disposed insaid casing and at least partially surrounding said light source toprotect the light source from excessive flexing and impact.
 18. Aliquid-tight impact resistant flexible marker lamp according to claim13, wherein said electrical connections comprise Insulated wire cableswith attached strain relief structure.
 19. A liquid-tight impactresistant flexible marker lamp according to claim 13, wherein saidcasing has one tinted generally transparent side and one pigmented lightblocking darker side.
 20. A liquid-tight impact resistant flexiblemarker lamp according to claim 13, and further comprising: generallyrigid elongate members to modify flexual characteristics of said casingto prevent impact damage to said light source.
 21. A liquid-tight impactresistant flexible marker lamp according to claim 13, wherein saidcasing comprises variable durometer elastomeric polymers.
 22. Aliquid-tight impact resistant flexible marker lamp according to claim13, and further including: casing mounting structure to support thecasing by said electrical connection when the casing is subjected tosubstantial impacts.
 23. A liquid-tight Impact resistant flexible markerlamp according to claim 13, wherein said wire harness comprises thermalheat sink means for said light emitting diodes.
 24. A liquid-tightimpact resistant flexible marker lamp according to claim 13 wherein thecasing comprises a plurality of regions differing in hardnesses andflexibilities.